Handle cross-thread weak persistents during global weak processing.

Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985
Committed: https://crrev.com/a71167e5645142b200f917bf26b7a546e36a3574
Cr-Commit-Position: refs/heads/master@{#402734}

[sof, 2016-06-28 21:03:52]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2016-06-28 21:03:52]

please take a look.

[sof, 2016-06-28 21:09:51]

Description was changed from

==========
Handle weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNode once the
weak reference points to an otherwise unreferenced object.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the weak persistents along with the 'weak cells'
during global weak processing.

R=
BUG=623985
==========

to

==========
Handle weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the weak persistents along with the 'weak cells'
during global weak processing.

R=
BUG=623985
==========

[sof, 2016-06-28 21:24:04]

Description was changed from

==========
Handle weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the weak persistents along with the 'weak cells'
during global weak processing.

R=
BUG=623985
==========

to

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the weak persistents along with the 'weak cells'
during global weak processing.

R=
BUG=623985
==========

[sof, 2016-06-28 21:24:57]

Description was changed from

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the weak persistents along with the 'weak cells'
during global weak processing.

R=
BUG=623985
==========

to

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985
==========

[haraken, 2016-06-29 00:41:54]

haraken@chromium.org changed reviewers:
+ haraken@chromium.org

[haraken, 2016-06-29 00:41:55]

https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Persistent.h (right):

https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Persistent.h:191:
visitor->registerWeakMembers(this, m_raw, handleWeakPersistent);

Is there any reason you don't want to move this one to global weak processing?

[sof, 2016-06-29 05:13:47]

https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Persistent.h (right):

https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Persistent.h:191:
visitor->registerWeakMembers(this, m_raw, handleWeakPersistent);
On 2016/06/29 00:41:54, haraken wrote:
> 
> Is there any reason you don't want to move this one to global weak processing?
> 

It would be untidy to do so, as Persistent<>s have a same-ThreadState
assumption, which is asserted for when freeing the PersistentNode.

[haraken, 2016-06-29 05:16:22]

On 2016/06/29 05:13:47, sof wrote:
>
https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
> File third_party/WebKit/Source/platform/heap/Persistent.h (right):
> 
>
https://codereview.chromium.org/2106863003/diff/20001/third_party/WebKit/Sour...
> third_party/WebKit/Source/platform/heap/Persistent.h:191:
> visitor->registerWeakMembers(this, m_raw, handleWeakPersistent);
> On 2016/06/29 00:41:54, haraken wrote:
> > 
> > Is there any reason you don't want to move this one to global weak
processing?
> > 
> 
> It would be untidy to do so, as Persistent<>s have a same-ThreadState
> assumption, which is asserted for when freeing the PersistentNode.

ok, LGTM

[sof, 2016-06-29 05:17:25]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-06-29 05:17:50]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[sof, 2016-06-29 05:20:12]

There's no shortage of subtlety and surprises when it comes to
CrossThread(Weak)Persistents.. :)

[commit-bot: I haz the power, 2016-06-29 05:21:25]

Description was changed from

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985
==========

to

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985
==========

[commit-bot: I haz the power, 2016-06-29 05:21:26]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-06-29 05:23:29]

Description was changed from

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985
==========

to

==========
Handle cross-thread weak persistents during global weak processing.

r401880 changed the handling of weak persistents, clearing
and releasing their underlying PersistentNodes once their
weak references point to otherwise unreferenced objects.

However, performing that weak processing step cannot reliably
be done as part of thread-local weak processing if the
weak persistent is a CrossThreadWeakPersistent<T> (CTWP) as the
object it refers to may reside on a different thread's heap than
where the CTWP resides. If both locations need to be accessed,
doing that as part of thread-local weak processing is too
late and unsafe.

Instead we process the cross-thread weak persistents along with the
'weak cells' during global weak processing. WeakPersistent<>s are
still handled during thread-local weak processing.

R=
BUG=623985

Committed: https://crrev.com/a71167e5645142b200f917bf26b7a546e36a3574
Cr-Commit-Position: refs/heads/master@{#402734}
==========

[commit-bot: I haz the power, 2016-06-29 05:23:31]

Patchset 2 (id:??) landed as
https://crrev.com/a71167e5645142b200f917bf26b7a546e36a3574
Cr-Commit-Position: refs/heads/master@{#402734}